How dark is the sky in the Czech Republic?
Sky darkness for 84 towns and parks in the Czech Republic, worked out from NASA satellite images of light at night (2025). 22 of them have skies of Bortle 4 or darker, where the Milky Way shows overhead. The darkest is Šumava National Park (21.58, Bortle 4), the brightest Prague (18.24, Bortle 8).
19
Bortle class, 1 pristine to 9 city center
park or dark-sky place
city
Numbers like 21.95 or 16.97 are the brightness of the sky overhead on a clear, moonless night, in mag/arcsec². The scale runs backwards: a lower number means a brighter sky, from about 22 for a natural sky to about 17 in a city center.
How the readings are made
Darkest skies in the Czech Republic
- Šumava National ParkPlzeň Region · Bortle 421.58
- Český les Protected Landscape AreaPlzeň Region · Bortle 421.41
- the Manětín Dark Sky ParkPlzeň Region · Bortle 421.38
- Jeseníky Protected Landscape AreaOlomouc Region · Bortle 421.36
- Třeboňsko Protected Landscape AreaSouth Bohemian Region · Bortle 421.33
Among the places on this site. Plenty of land between them is just as dark, with no town or park to name it by.